This application relies for priority upon Korean Patent Application No. 2001-87125, filed on Dec. 28, 2001, the contents of which are herein incorporated by reference in their entirety.
The present invention relates to a method for fabricating a semiconductor device used in a wafer cleaning process and, more particularly, to a method for drying a wafer subjected to a cleaning process.
As semiconductor devices are continuously scaled down, the wafer cleaning techniques have been diversified and increasingly significant. Particularly in a process for fabricating semiconductor devices having a fine structure, particles attached to a cleaned wafer, static electricity, watermarks, and linear particles have a great effect on subsequent processes. Therefore, what is needed is a wafer drying process.
There were suggested a spin dryer and an IPA vapor dryer. In drying a wafer, the spin dryer uses a centrifugal force while the IPA vapor dryer uses a low vapor pressure of isopropyle alcohol (IPA). However, the dryers cannot completely remove watermarks that occur on a wafer surface or between patterns. In order to avoid this problem, a Marangoni dryer has been widely used. The Marangoni dryer uses a difference between surface tenses of the IPA and water.
A drying process using the Marangoni effect will now be described in brief hereinbelow.
After wafers are rinsed out by de-ionized water (hereinafter referred to as xe2x80x9cDIWxe2x80x9d), the IPA vapor is fed to an upper interior space of a rinsing bath and the DIW is slowly withdrawn. Thus, the water is eliminated from a wafer surface. When the DIW is completely drained, the nitrogen of high temperature is fed thereinto to evaporate the DIW remaining on the wafer surface. Unfortunately, the evaporated DIW and residues including particles are not fully issued out. They cause the irregular liquid flow (turbulence) in the rinsing bath together with the nitrogen, so that the wafer surface is not uniformly dried and the water remains at a portion contacting with a wafer guide. In addition, since the Marangoni dryer cannot fundamentally prevent oxygen from reacting on the wafer, it cannot suppress formation of an oxide layer.
A feature of the present invention to provide a wafer drying method that fundamentally prevents oxygen from reacting on a wafer surface during a wafer drying process to suppress formation of an oxide layer.
Another feature of the present invention is to provide a wafer drying apparatus that improves a wafer drying efficiency.
To achieve these features, the present invention provides a method for drying a semiconductor substrate. The method comprises the steps of clearing the substrate by supplying a liquid into a processing bath of a chamber, decompressing an inside of the chamber, draining the liquid from the processing bath and injecting a first dry gas onto a surface of the liquid in the processing bath, and injecting a second dry gas onto the substrate after the liquid is completely drained therefrom. The second dry gas is nitrogen or carbon dioxide or dry air. A temperature of the second dry gas is between an ordinary temperature and 120xc2x0 C.
The inside of the chamber is decompressed by exhausting air from the chamber through a vacuum exhaust pipe installed at the cover. In the step of injecting the second dry gas, the second dry gas is vacuum-drained.
According to another aspect of the invention, a method of drying a semiconductor substrate comprises the steps of clearing the substrate by supplying a liquid into a processing bath of a chamber, injecting first dry gases onto a surface of the liquid supplied into the processing bath, draining the liquid from the processing bath so that the substrate is slowly exposed to the surface of the liquid, and injecting a second dry gas into the chamber and forcibly exhausting the gas in the chamber. The method further comprises a step of decompressing the inside of the chamber before injecting the first dry gas to exhaust air in the chamber. The air in the chamber is exhausted through an exhaust port installed at the cover. The step of exhausting the air in the chamber includes a step of supplying an inert gas into the chamber.
When the liquid is completely drained from the processing bath, the second dry gas is vertically injected from an upper part of the processing bath, and the second dry gas injected into the processing bath and vapor evaporated from a wafer surface by the second dry gas are forcibly exhausted to an exterior of the processing bath. The gas in the processing bath is exhausted through an exhaust pipe connected to a drain pipe where the liquid is drained. The second dry gas is injected after completely draining the liquid in the processing path. The second dry gas is an inert gas preheated at a temperature between an ordinary temperature and 120xc2x0 C., and the liquid is de-ionized water (DIW). The first dry gases are preheated alcohol vapor and nitrogen. The alcohol is one selected from the group consisting of methane alcohol, ethane alcohol, and isopropyle alcohol (IPA).